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  1. #1
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    Fabric for underquilts ?silinylon

    In contemplating the ultimate UQ, and having asked some questions elsewhere about minimilizing the design, I was wondering about using silinylon as the underface of a home made quilt (and normal sleeping bag nylon on the surface under the hammock). I've found some discussion about moisture/evaporation issues, which I understand with respect to a quilt or sleeping bag over the top of you, but, with an underquilt, it doesn't make sense to me. Heat travels upwards.........why would you get condenstation on the bottom layer?

    Some thoughts would be appreciated.

    Andrew A

  2. #2
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    Because moisture pervades the whole thing and condenses in the cooler portions (as you move through the insulation the temperature drops). So you'd end up with a pool of water in the bottom, or very damp insulation.

    For some synthetic insulations that would merely be unpleasant, with down it could easily be fatal.

    You want the insulation to be able to breathe. A sleeping bag may have significant moisture in it over the course of a night. Read about transpiration, the quantites of water your body produces are very large. Your sleep insulation system has to be able to handle it...

    My personal preference is a dual system. Down inner bag with breathable shell inside and out, covered with an outer bag with a WPB (waterproof breathable) liner and synthetic insulation (FWIW these are very hard to find, I made my own.). The idea is that the moisture stays warm enough to pass through the down bag, and the WPB liner of the synthetic bag and then condenses somewhere in the outer bag if it does at all. The result being drier down protected by waterproof outer bag that can be easily dried and is less susceptible to water problems. Works well fro me in all sorts of situations.

    Damp rainy cool weather (2C and raining) , cold frosty dry weather (-35C and crisp), I use the light WPB lined bag for straight summer use (>15C rain or shine).

    Thats how I would do the UQ if you're worried about external moisture coming up from below.
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  3. #3
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    Quote Originally Posted by Rapt View Post
    Because moisture pervades the whole thing and condenses in the cooler portions (as you move through the insulation the temperature drops). So you'd end up with a pool of water in the bottom, or very damp insulation.

    For some synthetic insulations that would merely be unpleasant, with down it could easily be fatal.

    You want the insulation to be able to breathe. A sleeping bag may have significant moisture in it over the course of a night. Read about transpiration, the quantites of water your body produces are very large. Your sleep insulation system has to be able to handle it...

    My personal preference is a dual system. Down inner bag with breathable shell inside and out, covered with an outer bag with a WPB (waterproof breathable) liner and synthetic insulation (FWIW these are very hard to find, I made my own.). The idea is that the moisture stays warm enough to pass through the down bag, and the WPB liner of the synthetic bag and then condenses somewhere in the outer bag if it does at all. The result being drier down protected by waterproof outer bag that can be easily dried and is less susceptible to water problems. Works well fro me in all sorts of situations.

    Damp rainy cool weather (2C and raining) , cold frosty dry weather (-35C and crisp), I use the light WPB lined bag for straight summer use (>15C rain or shine).

    Thats how I would do the UQ if you're worried about external moisture coming up from below.
    Further information/thread bout your creation? Interested in what you used for the WPB liner..

  4. #4
    Senior Member lymphocytosis's Avatar
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    The only time a vapor barrier really helps (as far as I am aware) is in very cold weather. When in freezing temperatures, any moisture has a tendency to freeze in your insulation before it gets a chance to evaporate, but it takes practice to know how to use one properly, and then you would generally physically get inside a separate vapor barrier that you could shake the frozen condensation off in the morning. At any other time, the vapor barrier is a pain, and you end up wet.

    That being said one of the best trusted quilt cottage shops makes UQs with nonbreathable cuben fiber. But I'm pretty sure that was done as a weight saving measure for gram weenies, not to be a vapor barrier. Stormcrow did extensive testing to determine whether the needle holes were sufficient to allow the quilt to breathe and not hold moisture in the down.
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  5. #5
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    I don't have a thread as this was created long ago... About 1994 or '95.

    Its a full "barrel" style sleeping bag with a light quallofil insulation layer (about 1" or so thick, and the WPB lining is two layer Gore-tex lining material. Basically the inside two layers of a three ply goretex product. The membrane with an tricot bonded to it. Outer shell is a light nylon taffeta.

    Benefits are waterproof, windproof, breathable, and feels good against the skin when sleeping against it.

    Sized to have a nice fit over my down bag, with extra length and will zip together for a top/bottom reversible 3 season setup for two.
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  6. #6
    Senior Member OneThing's Avatar
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    JRB Weather Shields

    Quote Originally Posted by Rapt View Post
    My personal preference is a dual system. Down inner bag with breathable shell inside and out, covered with an outer bag with a WPB (waterproof breathable) liner and synthetic insulation (FWIW these are very hard to find, I made my own.). The idea is that the moisture stays warm enough to pass through the down bag, and the WPB liner of the synthetic bag and then condenses somewhere in the outer bag if it does at all. The result being drier down protected by waterproof outer bag that can be easily dried and is less susceptible to water problems. Works well fro me in all sorts of situations..
    Back in 2004 I purchased a The JRB Weather Shields. They no longer have the original set. One covered the UQ and the other went over the top of your sleeping bag. Both were made of microporous polypropylene.

    Sgt Rock did a write up on them here. http://hikinghq.net/hammock/jacks_weathershield.html

    I used them for about a year and found them for the most part to work well in most situations.

    Is this what you were referring to in your answer?

    I wasn't fond of the color, and they are a little skimpy in material, which requires being very careful on not pulling too hard when setting up the bottom on the hammock.

    I do see that JRB have a new one, but the price for one is about what it was for two back in 2004. Lucky for me, both of mine are still in great shape.

    I'm wondering if a sock made of this would work for under and over the ridgeline.

  7. #7
    Senior Member OneThing's Avatar
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    VB for the Whole Body

    Quote Originally Posted by lymphocytosis View Post
    The only time a vapor barrier really helps (as far as I am aware) is in very cold weather. When in freezing temperatures, any moisture has a tendency to freeze in your insulation before it gets a chance to evaporate, but it takes practice to know how to use one properly, and then you would generally physically get inside a separate vapor barrier that you could shake the frozen condensation off in the morning. At any other time, the vapor barrier is a pain, and you end up wet.

    That being said one of the best trusted quilt cottage shops makes UQs with nonbreathable cuben fiber. But I'm pretty sure that was done as a weight saving measure for gram weenies, not to be a vapor barrier. Stormcrow did extensive testing to determine whether the needle holes were sufficient to allow the quilt to breathe and not hold moisture in the down.
    I've tried a number of VB. I started with the STEPHENSON NO SWEAT SHIRT. I added a pair of WP rain Pants & WP socks. I also tried a WP sleeping bag which you get into naked, or silk. You close it up around your neck and it's a sauna.
    Needless to say, it has it's pro's and cons. You will stay warm as long as heat is coming from your body. Once the furnace inside you stops, all the water inside gets very cold. I would bring one candy bar and eat it in the middle of the night to keep the furnace going.

    In the morning, you get out, take everything off & turn it inside out to let all the water drain. (You could get at least 1/2 liter)

    Here's a few of the pros & cons with it.
    Pro's
    1. Your sleeping bag, UQ stay bone dry.
    2. As long as the inside furnace is going, you can get by with a lower rated sleeping bag on top.


    Cons
    1. Fire goes out, your wet and freezing.
    2. VB shirt takes forever to dry on the trail without sunlight.
    3. Candy bar inside hammock is like inviting a Bear to dinner.
    4. Middle to the night wiz = Forget about it.

    It did save my butt one night on the AT when water filled my HH (Rainfly didn't cover part of HH) during a heavy cold downpour while eating dinner. Everything I had was drenched. The temps dropped down to about 35f that night with high winds. Not the best sleep but I survived.

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